High-voltage regulator



oct; 7', 1952 w. H. NELSON HIGH-VOLTAGE REGULATOR 2 SHEETS-SHEET` l Filed March 8, 1949 A VVVV Oct. 7, 1952 w. H. NELSON HIGH-VOLTAGE REGULATOR 2 SHEETS--SHEET 2 Filed March 8, 1949 Patented Oct. 7, 191,52

HIGH-,VOLTAGE REGULATOR Walter H. Nelson, Cadillac, Mich., assignor to the United States of America. as represented by the United States Atomic EnergyvCommission Application March; 8, 1949, Serial No. 80,269 (c1. 32a- 22) i Claims. l

This invention relates to a high rvoltage regulator and more particularly to an improved high voltage regulator using internal negative feedback within the regulator amplifier proper.

An important problem whichhas long confronted engineers in the design of precision high voltage regulators is that of avoiding oscillation within the regulator circuit.

VA simplified approach to the problemof 180 phaseshift, which is inevitable when a two-stage amplifier is used, is to minimize -allrresistance capacitance time constants in the regulator circuitiexcept that 'of the output. This methodis quite effective but results in excessive capacitance in the output of the high voltage supply which is undesirable where the load is characterized byk occasional short circuits. Moving the controlling time constant to another location in the network makes the impedance, looking back into the. reg' ulator circuit inductive in nature. which is also undesirable for certain applications.

A methodL of reducing the` capacitance required in the output ofa regulated high voltage supply called the phase advance method was tried, :wherein a resonant circuit was introduced into the regulator network in such a way as to avoid enclosing thev point (1,70) on a polar diagram of the quantity a; This effect is possible because of the fact that a resonant circuit ex@- hibits a phase shift below resonance in a direction opposite to that shown above resonance. The use yof this phase advance circuit permits a much smaller output capacitance, which means a faster regulator response. but this circuit is still notvindependent of the output capacitance because a smaller output capacitance requires a higher resonant frequency for the resonant circuit. v f

With these disadvantages of the usual high voltage regulator in mind, the improved regulator amplifier circuit as hereinafter described provides an apparatus wherein the regulator is simplified and the margin against oscillation is made. substantially independent of the output capacitance. This is accomplished by applying frequency selective negative feedback within the regulatory amplifier proper. This feedback is such as to provide two ylevels of amplification, both with low phase shift. One gain level is high at low frequencies and the other gain level is low at high frequencies with a transition range in which `the vmaximum phase shift is 90. Thus the phase shift caused by the feedback network decreases with increasing frequency as thelow gain y plateau -is approached. The smallerl the f amplifier having internal negativefeedback, said amplifier having its input associated lwith the load circuit supplied by thehigh voltage regulator.- f i Another object of this invention isto provide an improved and simplified high voltage reg-,- ulator using a series-connected losser tube controlled by a negative feedback amplifier wherein the output capacitance is not a critical factor in the prevention of self-oscillation.

Another object of this invention is to provide an improved and simplied high voltage regulator having a series-connected losser tube controlled by a feedback amplier, the gain of which is substantially reduced above a certain frequency but maintained at a high value between this frequency and zero frequency.

Still another object of this invention is to provide Van improved and simplified high voltage regulator having a series-connected losser tube controlled by an amplier having a gain characteristic such that the possibility of oscillation around the regulator loop is minimized. 1

A stillfurther object of this invention is to provide an improved and simplified high voltage regulator having a series-connected losser tube. controlled by a negative feedback amplifier havinga minimum phase shift around the regulator loop.

Other and further objects ofk this invention Will be apparent to those skilled in theart to whichy it pertains, upon consideration of the following specications and drawings in which:

Figure 1 is a schematic wiring diagramfof a preferred embodiment of alhigh voltage regulator of the direct coupled type; and i Fig. 2 is a schematic wiring diagram'of a second embodiment of a high voltage regulator of the direct coupledtype. v l

Referring to Fig. 1 in detail there is shown one embodiment of the high voltage regulator of this invention in schematic form. A conventional high voltage rectifier unit. Il has a negative terminal l-2,connected directly to the cathodeof a diode current limiting vacuum tube I3, while the 3 anode of the vacuum tube I3 is connected to an output terminal I4. The output terminal I4 is connected to ground bus I6 by a series network comprising a resistor |1 and a condenser I8. The cathode of the diode limiter tube I3 is by-passed to the ground bus I6 by a condenser I9. A positive terminal 2| of the high voltage rectifier unit I| is connected directly" to the anod'e 'triod'e regulator tube 22 -by aconductor v23,"Th'e cath ode of regulator tube 22 is connected to the ground bus I6 by a conductor 24. A diode tube 26 has its anode connected to the control 4grid of regulator tube 22, and its cathode is connected to the cathode of such tube. A spark gap 21 is valso connected between the control grid andlth'ec'athf ode of the regulator tube 22 toprevent'surges from damaging the tube. regulator tube 22 is connected to a negative ter minal 28 of a low voltage power supply 29 by a conductor 3 I.

This low voltage power supply 29 is a convene tional,.fullwave alternating current rectifier unit comprising a transformer 32 and ap'air of diode vacuum tubes 33 and 34. The output 'of rectifier unit 29 is applied to a pi-.section smoothing filter comprising an ironcore inducta'nce 36 in series with a pair of lter condensers 31, 38. ,This nla ter is shunted by a resistor 39 for discharging the filter condensers 31 and 38 when the rectifier unit is not energized. The direct current voltage sup'- plied by low -voltage supply 29 is obtainable at negative terminal 28 and positive terminal 4| The positive terminal 4| of the low voltage sup'- ply 29 is connected to the anode of a pentode vacuum tube 43 by a conductor 44; the cathode of the pentode 43 is connectedtov the ground busl I 6 by a conductor 46. The suppressorgrid of this tube 43 is connected by conductor 41 to itscathode. The screen grid voltageof pentode 43V is supplied from a second low voltage supply 43 by aconductor 49.

, The low voltage supply 48 comprises a power transformer 5I, a rectifier tube 52, and a' filter network made up of two iron core inductances 53' and 54 and iilter condensers 56 and 51 connected thereto as shown. The voltage of this supply 48 is obtainable at terminals 6| and 62.' A voltage divider comprising series-connected resistors 63l and 64 is connected across the terminals 8|V and 62. A tap on resistor 64 is connected through a resistor 66 to the control grid of pentode tube 43 and. 'also to the anode .of an input pentode 61 which is connected tothe control grid of pentode 43 by conductor 68, -for supplying the proper voltages thereto. Aresistor 69 connectsthe positive terminal 6I or the secondlow voltage supply; 48 to the negative terminal 28 of the rst iowv'oltag supply 29. A negative feedback networkv comfprisinga series-connected.- condenser v1| and 4resistor12 is connected between the grid of regulator triode 22 and the cathode of. the input pentode tube 61.r The cathode and the suppress-or grid of this pentode tube 81 are connected together' by` a conductorV 13. The vcathode. ofA pentode 61 isV con'- nected through a resistor 14 tothe` negative ter'- minal 16 of the low voltage standard" now to b described.

The low voltage standard 11 is comprisedof a trans-former 18, a diode rectifier-tube19;and-a pisection filter made'up of the ironcorefinductance 8| and condensers Bland 83. 1 Acoden'ser 84 is connected betweenthe' negative terr'rin'al 16 and the ground bus I6; A conductor- 86. connects- The control gridjof` 4 anode of a pentode 88. The anode and screen g-rid of pentode 88 are connected together by a conductor 89. The cathode of pentode 88 is connected to the ground bus I6 by conductor 9|. The control grid of pentode 88 is connected to the ground bus I6 by a resistor 92 and also to the anode of a pentode tube 93 by conductor 94.

fAvoltag ditider comprising 'series-connected resistors 96, 91; and 98 is-oonnected between the negative terminal 16 and the ground bus I6. The junction between resistors 96 and 91 is connected to the ,cathode of pentode 93 by conductor 99 while the junction between resistors 91 and 98 .i's connected to the screen grid of the same pentode 93 by conductor |0I.

A series-connected gaseous voltage regulator tube |02 and its current limiting resistor |03 are also connected between the negative terminal 16 and the ground bus-I6'. The junction between the gaseous regulator tube |02 and the current limiting resistor |03 is connected to the control grid of the pentode 9.3 by-conductor |04; A condenser |05 is connected between the negative terminal 16 and the groundabus` I6, as is another voltage` divider comprising theseries-connected resistors I06:and

|01., A tap on .resistor |01 connects' through a resistorAr |08*v tooner end ora resistor |I| and a connected to the negative high voltage terminal I4- by a conductor I|3. The junction |09 between.

the-resistorvl08 and shunt-connected'resistor ||I and .condenser I I2, isconnected through another shunt networkcomprising a resistor I I5 and coi1= denser |I6 connected to the4 control grid ofthe pentode Atube 61.- The above-mentioned junction point |09 is alsowco'nnected to the negative terminal 16 of the voltage standard 11 bythe by-pass condenser II1.vl`

A .gaseous voltage'regulator tube ||9 shunted by a by-pass condenser |2I .is connected between theV screen gridof the ypentode tube 61"and the negative terminal 16 of the voltage standard 11, for maintaining the screen grid voltage constant. The screen gridof the pentode tube. 81 is also connected to thek groun'd bus I6 :by a resistor |22'.

With the foregoing interconn'ectionv ofr compo'- nents inzmind.- l'et us r'iow consider the operation of the -highvoltage fregulator described.4 Terminals thek ground busts. f

.1r win be apparent met suesy 10aa vcefaleaier;'

is also across the two regulator vacuum tubes I3 inglaactionsmtaking place' 'across the output of' as' a current liii'iitertoll'ev'e'nt excessive current from flowing through the circuit in@ case the 10aa shouid become shorfcirsuited. 'nus limiting tic--y tion is'accomplishd by operating th dio I3-l ing voltage below its'normai value-through the' provision oi-me'ans 'well l'fn'own in the-art. Sec= ondly.` a concurrent'r'egu-lating action is provided by the regulator'tube' 22 ywhich acts" as a losser tube and tends to keep theV output'voitag-betweei terminal' I4f'and the ground bus I6 Vsubs'taitially constant. Tube 22, therefore, acts asa variable electronic Simped'ancelthe Value' of which cn# trolled by the voltage;v applied to, the: control grid ihsrofw@ Two safety devices are shown as connected between they controlgrid and the cathode of the regulator tube 22. The sparkgap 2'! isto protect the regulator tube 22 from any high voltage surges which might appear in this part of the circuit, while the diode 2t which is also connected between the control grid and the cathode of the regulator tube 22 prevents the control grid from becoming positive with respect to the cathode, thereby preventing an excessive currentfrom flowing through the regulator tube.

-,The high `voltage divider network previously de-y scribed and comprising resistorsy |5355, lill, |23 and |I| has one end connected `to the ground bus ift and one end connected through the conductor H3 to the high voltage output terminal itl.

age rectifier I .Thestandard voltage supply Il is y also connected across resistors Hi8 and lill and impresses a voltage on these resistors which is opposite in polarity to that impressed by the high Voltage rectifier il. By the selection of an appropriate tap or by correctly positioning a slider on resistor itil a predetermined voltage or" correct magnitude and polarity may be impressed on the control grid of pentode 6l.

Since the standard voltage obtained from the supply is maintained highly constant, the Voltage at the junction point |09 which is due to the standard voltage is also constant. The second voltage which is of opposite polarity to the standard voltage that is also present at the point idd is a sample of the voltage to beregulated and con tains various excursions due to Variations in load current, line voltage, etc. The comparison of this sample voltage andthe standard voltage results in a, low voltage containing all the variations of the sample voltage. These variations are f amplified by the pentode El andpassed on to the control grid of the pentode 4S by the conductor |58; hereA the signal is amplified further and finally coupled tothe control grid of the regulator tube 22 through the power. supply 29.

' The signal voltage on the control grid of the regulator tube 22 is coupled through a frequency discriminating network comprisingv condenser l'i and resistor 12 to the cathode of the input pentode Sl to provide negative feedback or a desired freduency characteristic. This feedback network is, chosen so that they gain of the ampliiier is high at low frequencies, and low at high frequencies; preferably with a transition range where the gaindrops'oit at the rate of six decibels per octave.

,Now it Will be seen that if the high voltage across the load increases in magnitude there will be a differential increase in voltage applied to the input of the direct coupled amplifier due to the voltage dividing action of resistors lll,r |68, lilll and ma. This signal voltage is then amplifled by the vacuum tubes Sl' and d3 and applied to the control grid of the regulator tube 22 with the correct polarity and magnitude to increase the impedance or losser action of the losser tube 22 so as to increase the voltage .drop thereacross and absorb thefextra voltage, thereby maintaining. the load voltage substantially constant. y

Similarly, if the high voltage acrossvthe vload decreases in magnitude, there is a differential decrease in the voltage impressed on the control grid of the vacuum tube 6l due to the voltage dividing action of resistors |98, |07 and |06. This differential voltage is ampliiied by the vacuum tubes El and 43 and applied to the control grid of the regulator tube 22 and is of such magnitude and polarity as to decreasetheinternal resistance or losser action ofthe regulatory tube 22. thereby lowering the voltagedrop `across this tube` rand increasing the output voltage obtainable at |3 in thenegative lead as previously described, the Y outputcurrent'is prevented from becoming too large in case of a short circuit in a load connected between the terminal I4 and the groundbus I6. l'he regulator is preventedfrom breaking into self-sustaining oscillation 'by the negative feedback network comprisingfthe condenser 1| and the resistor l2, which maintains the gain high at low frequencies and low at the high frequencies. A second embodiment of my invention is shown in Fig. 2. nthis embodiment a` highN voltage rectifier and filter 26|) has a negative terminal 2d! connected to acenter tapV on the secondary winding of a cathode heating. transformer 282 by a conductor 293. The transformer 2il2 has its secondary directly connected to an emission limited diode Zelt and suppliescathode power thereto. A condenser 2l'i`is connectedfbetween the center tap on the secondary winding of transformer -292 and a ground bus 208. The primary winding of Vtransformer 2512 is connected by means of conductors 2|! and 2|2v to thek terminals 2|3 and 2 ifi for receiving suitable power therefrom. These terminals 2|3 and Ziriare also connected to theA primary winding of a second iilament heating transformer 2|6 by conductors 2H and 2 i8 forvsupplyingsuitable power thereto. Terminals 2 i9 ofthe high voltage rectier'unit 280 are connected by conductors 22| to terminals y222 which are in turn connected to a suitable source of power for energizing the high voltage rectifier and filter unit 200.

A positive terminal 223, off the high voltage rectifier 222 is connected by a resistor 224to the anode` of a series losser` triode tube226.. The cathodeof vacuum tube'226 is connected directly to the secondarywinding of the transformer 2 I6. The center tap 227i of transformer 2|6 isconnected to the ground bus 298 by a conductor 228. The anode of the current limiting diode2t8 isy connected through conductor 229 to the knegative output terminal 23l. A suitable load 222 is connected between the terminal 23|'and the rground bus 228. The anode of diode 205 is also connected to one terminal v233,. of va .compensated voltage divider unit 231i by a conductor 235. A second terminal 23''fof the compensated voltage divider 234 i'slconnected througha conductor 232 to a terminal 239. The latterr is'connected to a positive terminal 24| of a voltage standard 242 by a-'sliunt-connected networkA `comprising a resistor 2f-'i3 and a condenserA 2132,'l A negative terminal 246 ofthe voltage standard 2112 is connected to the ground bus.. Edeby a conductor 2li?. A

shunt-connected netart/ori;k 'comprising a resistor. 242- and a 'condenser is connected The input 'terminal 251 Af the tirt coupled apli-''er 252 'is io'Ii-'I'lecte'd to the rcontrol'girvl fof a tentons vacuum tube 2 se by a resistor i251. 'me suppressor lgrid *of the pentb'd '-2 5651s ji:'Siiri'zlied 'to the cathode of this t'b by a cbn'dl'i'to' '258 f the cathode is `in turn `cr'i'iirr'cted t the bus 4208 through a shunt ntwrli 'ciprisiig fan inductaric v25'!! aia-d f resistor v"260. The s'ei'e'n grid of the pentode 2 f`5'is connected to a tp'fon battery f2'62 v"by a 'cn' uctr 26-3 for rc'eii/inr i the The "tode 're ive's its proper operating toit'- afge fr the positive-end of battery 12%'2 'thr'ugh ajresis'to'r 2'6'1. The ng'atiye end of the battery 262 directly cinctd to the ground bufs20`8 by conductor 26'6'. The anode 'of pentodeZSB is al's''on-necte'd to the controlgiid of arhultigrid Vacuum 'tube 261 by the shunt etworkfcinp'ri'sing 'a condenser 268 and a 'resistor 259. The con: tr'ol grid receives its correct operating bias Volta'g through 'resistor 211 rin the ngative end of a battery 212; The cathode off tub'e 25T is connected toa ta'p 213 on the battery 212 Oyfa conductor 214'. The screen Vgrid 'of the tube 251 receives lits operating yroltaige from 'a more posi'- ti'v'e vi`1'olt`a`g`e 'tap 216 through a 'conductor 211'. The battery '-2152 has its positive endco'nricted directly to the 'ground bus 2il'8 byconduc'tr 21'8.

The anode of theyaiui'n tube 261 is connected to 'the output trrninal 279 of the direct `coupled aii'pliier l252 by the conductor 281-. -o'utf put terminal '219 isfcb'nnecte 'to the control grid of the regulator time 2-25 by a conductqrjzez for suppl-Ying -the 'control Vlte thereto. The out; put terminal 219 is connected back through aresi'st'ori? 83 to the cathode of the input pentode 256 "order tof back 'aportion of the output sig'- nal. The' actual negative feedback loop coin-'- prises the 'resi-'Stor 2B-3, the'shunt circuit burnpiisifig the resistor 260ya1d-th lrlduCta-ice 2519. The 'anode 'of the tube 261 also rc'eires its operating 'voltage from vthe battery 212 throu'gh this above-mentioned feedback loop. u

' The 'operation 'of this secche embodiment wm now be discussed. The terminals '222; 21-3 'and 2H are corrnecte'd to vsuitable sources of power for Aenergiz'zi'r'ig the various components of the reg; ul'at'or. The output voltage 'of the rectifier unit 2110 'is "applied to the loa-'d connected between t'erL minal 2`3`| and 'the ground busl-208 through ah mission limited diode 5236-, 'which acts t6 rlnt an excessive -:dow of current in 'case of "short circuits 'in-'the' 10a-d 'circuit and through the "S ries regulator tube 226-, which acts toreg'ulat the voltage across the load.

Since the voltage standard 242 is connected in opposition to the voltage produced by the high Voltage rectifierA unit 200;, it is seen that the voltage at the -junction 239 Y is a low negative voltage which is applied to the input terminal 25| of the direct coupled amplifier 252 through a frequency compensated coupling network comprising the resistor 248 and the *condenser 249. The frquacrrestnse curve fof the direct edupled airibli'er 252 has been V"ufariei by 'using ir; quen'ey responsiyenegativ feedback so as, to profvide two x'amplication levels; thehgain being high at the low frequencies 'and low at the high ffrquncis orfrtbiy with a i transition fridge' in between Where the attenuation is six decibels per octave. I e

AThe diie'rential voltage applied to the input terminal 25| is produced by cbm-paring `A-a'sanpl of 'the highv voltage across the load 'with 'the standard 'voltage '242. `This differential signal Voltage vhasall of the voltage variations that -ar'e preseutin the output o'f the high 'voltage fectie'r unit 200 superimposed upon it. Thse Voltage variations are amplified Hy the direct coupled amplifier r252 and "applied to the 'control "grid of the regulator losser 'tube 225 'of s'uch magnitude and 'sign as to cause the interna-l i'indar'icebf the regulator -losse'r' tube to change, thereby ducin'g a variable voltage drop between thlposltive terminal Y223 'of Athe 'r'ectier unit 200 and th ground bus 208. This Variable voltage drop 'when correctly applied causes the load voltage fa'ppeaing between the terminal 2-3'! and the ground Abus 208 to remain substantially constant.

In both 'embodiments of this invention a sani ple 'of the high `voltage is compared with a stand'- ard voltageand a differential voltage is produced containing -any variations which were loriginally present in the vhigh voltage This differential voltage and the superimposed variations are ampli'ed by the direct coupled amplier comprising tubes '67 and 43 (Fig. 1) and the direct Ycoupled amplifier 252 (Fig. 2l,y both amplifiers using internal negative feedback, and the resulting voltage applied to the control grid 'of series type losser tubes 22 -(Fig-1") and 2'26 ('Fig. 2). 4These series losser tubes act as variable 'electronic ini"- pedances of the correct magnitude to 'kcepthe output voltage of the high voltage regulators 'depicted in Figs. l1 and 2 `vsubstantially constant. Both regulatorsgincludean emission limited ldiode (I3 Fig. Y1 and -20'6 Fig. 2)' whicl1'serves to limit the maximum current which may be drawn yfrom the high vol-tage rectier u-nit.

It will be apparent that the two direct coupled amplifiers disclosed in Figs. -1 and t2 differ somewhat -in the Way that the negative -feedbackis inserted i. .f

In Fig. -l the negative feedback voltagefed back to the input is determi-ned` by the condenser 'l.|-, the resistor 12, and the cathode resistor 7,4. At the low frequencies the yoltage fed -back tothe cathode resistor 14 is negligib1e, as the condenser` 'Il offers a large infimedancey at these frequencies. and in this range the Ygain is jhigh.` At the lhigh frequencies the impedance of the condenser 11 is small compared to the resistors 'I2 and lHt-and these resistors are the determining vfactor; in this range the amplification is low. 'There 'is 'a transition range where 'the impdanci'of 'the cndense'r :Il is comparable 'to that f th'e're'si'str's l2 and T4, and in 'this range the "attenuatii p r# c'ee'ds at the lrate of six 'decibels per octave. The foregoing method using condenser's and "resistors is considered preferable.

It will `be noted that 'in the second embodiment shown in Fig- 2 the negative feedback loop inL clud'es rthe resistor 283 -and the shunt circuit 'in the cathode circuit of tube 25B which comprisesA the resistor 266 and the inductanc 25B. `At the lo'w frequencies the feedback Voltage developed in the cathode circuit is very small due tothe fact that the inductivereactance o f the indutance 259 is nsmall and Athe cathode of tube 256 is virtually connected to the ground bus 20'8. A't the high frequencies where the inductive rctance fv tiiineuctance 25a is large compared to die resistor z'so, the negatiyenreedbek is determined by the resistors zas and 26o, these resistors Being' r9' correctly proportioned to make Athe amplification ,low at thehigh frequencies. `VThe phase shiftis also small because the feedback network at the high frequencies is nearly purely resistive in nature.

In' the frequency range where the reactance of the inductance 255i is comparable to the/resistanceof-the resistor 26B, the attenuation-due' to feedback is preferably `about six decibels per octave. In this range the phase shift is limited to 9OfJ when attenuation proceedsr at the six decibels per' octave rate. Y

As mentioned above the method of introducing the negative feedback disclosed in Fig. l is the preferred method, as the method disclosed in Fig. 2 uses an inductance in the cathode circuit of the input stage (vacuum tube 256 Fig. 2) of the amplifier 252 (Fig. 2), and this inductance 259 must be well shielded if hum is to be kept to a satisfactorily low level.

Although I have described my invention with respect to two particular embodiments thereof, it is not limited to these embodiments nor otherwise, except by the terms of the following claims.

What is claimed is:

1. In a high voltage regulator of the direct coupled type and adapted to be connected to a source of voltage to be regulated and a load circuit requiring a constant voltage, the combination comprising a variable impedance means serially connected with said load circuit across said source of unregulated voltage, a voltage dividing network, a source of standard voltage connected to said voltage dividing network to provide a differential voltage, and a broadband direct coupled amplier having a negative feedback circuit therein, said amplifier being connected to said voltage dividing network for receiving said differential voltage therefrom and also connected to said variable impedance, said feedback circuit comprising resistive and reactive elements forming a high impedance at low frequencies and a low impedance at high frequencies, said amplifier serving to apply an amplified differential voltage of such sign and magnitude to said variable impedance as to cause said variable impedance to maintain said load voltage substantially constant.

2. In a voltage regulator of the high voltage direct coupled type and adapted to be connected to a source of high voltage to be regulated and a load circuit requiring a constant voltage, the combination comprising a variable electronic impedance serially connecte-d with said load circuit across said unregulated voltage source, a voltage dividing network connected across said load for obtaining a sample of the voltage thereacross, a source of standard voltage connected to said voltage dividing network to provide a differential voltage, broadband amplifying means connected to said voltage dividing network for amplifying said differential voltage, and a resistive and reactive network connected between the output and input of said amplifying means for negatively feeding back a portion of the voltage at said output dependent upon the frequency response of the elements of said network, said variable electronic impedance being connected to said amplifying means for receiving said amplied differential voltage therefrom, said amplified differential voltage when applied to said variable electronic impedance being translated into a varying voltage drop whereby said load voltage is kept substantially constant.

3. In a high voltage regulator cf the direct the voltage across coupled type andadapted to be connected toa source of high voltage to be regulated and a load circuit requiring ka constant voltage, the combination comprising a' series-regulator tube containing at least a cathode, an anode, and a control grid serially connected with said load circuit across said source of unregulated voltage, a voltage dividing networkconnected acrosssaid load circuit for obtaining a sample of. the high voltage thereacross, a source of standard voltage connected tosaid voltage dividing networkto provide a differential voltage, and a broadband direct ccuplediam'plier having a negative feedback circuittherein for amplifying said differential voltage produced by comparing said sample voltage and said standard voltage, said feedback circuit comprising a resistance and reactance network and having a frequency response characteristic determined by the values of the elements thereof to provide a high impedance at low frequencies and a low impedance at high frequencies, said series regulator tube being connected to said amplier for receiving said amplied differential voltage therefrom, said series regulator tube changing its internal impedance in response to said amplified differential voltage so as to keep said Aload substantially constant.

4. In a high voltage regulator of the direct coupled type and adapted to be connected to a source of voltage to be regulated and a load circuit requiring a constant voltage, the combination comprising a series regulator tube containing at least a cathode, an anode, and a control grid, said anode being connected to the positive terminal of said source of voltage to be regulated, said cathode being connected to one side of said load, the negative terminal of said source of voltage to be regulated being connected to the remaining side of said load, a voltage dividing network connected across said load for sampling the voltage 'thereacrosa a standard voltage connected across a portion of said Voltage dividing network to provide a differential voltage by comparison of said sample voltage and said standard voltage, a direct coupled broadband amplifier having an input, an output, first and second amplier tubes and a second source of power, said amplifier having its input connected to said voltage dividing f network for receiving said differential voltage therefrom, the output of said amplifier being connected through said second source of power to the control grid of said series regulator tube; and a resistance-capacitance network connected between the output and the input of said amplifier so as to provide negative feedback therein for providing a predetermined gain vs, frequency characteristic within said ampliiier.

5. In a high voltage regulator of the direct coupled type and adapted to be connected to a source of voltage to be regulated and a load circuit requiring a constant voltage, the combination comprising a regulator tube containing at least acathode, an anode, and a control grid; the anode of said regulator tube being connected to the positive terminal of said source of voltage to be regulated, said cathode being connected to one end of said load circuit, the negative terminal of said source of voltage to be regulated being coupled to the other end of said load circuit; a voltage dividing network and a source of standard voltage serially connected across said load circuit for producing a differential voltage by comparing said load voltage and said stan-dard voltage, a direct coupled broadband amplifier comprising 11 12 nrsf; mdseeend ampliertubes; saidrstfmpli* I BEFEBENGESF CITED mMue'haVigf its'contml gndnn'ectd t@ Said l'I'flefollowing references are off record in, me

voltage` dividing.VV rietworkrzrtoreceive said.: dit me of thisfpatengg. feremial voltage ther-efraimr said'. rstf; amplifier tube having aus inductive; cathode: circuit; the 5 UNITED STATES PATENTS anode-of said. secondi amplier tube;A being eorr- Number: Name 1 Date ne'cbedt'o. the control. gridot said regulator tube, 2343430.69? G01dberg...e -.fe.- Jan. 6,119.48 andi a;v resistor' connectingrbetween sadandde of 2,510,6835 Carpentier June161950 said secondi ari'ip'lifie'r"ubveA andv Said cathode of 1 1 f said. rst amplifier tube, said resistor and said 10 FOREIGN PATENTS ,inductive cathodeicircit forming'a'negative fe'ed- Number Gountfry. Date back network'. fr. providingV a desired gaminv vs'. 536615 Great Bntam -"-v May' 21111941 frequency characteristic Within. said amplifier.

WALTER H. NELSQN.Y 

